Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$178.64	10.121%	$196.7202	$196.72	$196.70	$196.70
Purchase #2	$18.51	11.426%	$20.625	$20.63	$20.65	$20.60
Purchase #3	$63.31	13.532%	$71.8771	$71.88	$71.90	$71.90
Purchase #4	$20.53	5.147%	$21.5867	$21.59	$21.60	$21.60
Purchase #5	$226.46	4.160%	$235.8807	$235.88	$235.90	$235.90
Purchase #6	$170.50	6.784%	$182.0667	$182.07	$182.05	$182.10
Purchase #7	$58.74	13.180%	$66.4819	$66.48	$66.50	$66.50
7 purchase totals =	$736.69		$795.2383	$795.25	$795.30	$795.30